Ruth - Chapter 1

This book is the story of a woman from Moab, named Ruth.  She is one of the few women named in the genealogy of Jesus in Matthew chapter 1:

Salmon the father of Boaz, whose mother was Rahab, Boaz the father of Obed, whose mother was Ruth, Obed the father of Jesse, and Jesse the father of King David.

Ruth was therefore the great-grandmother of King David, and although she was a gentile she is part of Jesus' family tree.